The order of the HTML should be used to determine the order of the CSS sections. CSS files can sometimes be large and commands difficult to find. Having some correlation between the HTML and CSS file makes it easier to locate how an element is being styled.

Know when to use elements, ids and classes

Using the correct selector type means your CSS file can be significantly reduced in size:

Elements – Elements such as body, (<body>), paragraphs, (<p>) and headings, (<h1>,<h2> etc.) should be used to define general rules

Ids – These are unique identifiers and should only be used once within a document. Ids should be used to style major structural sections of a web page such as the header or the footer.

Classes – These can be used on any type of HTML element.

Too many ids or classes can overload the HTML and the CSS files unnecessarily. Try and define as many rules as possible by referencing elements and/or ids by nesting the selectors.

Imagine the following HTML code:

<ul id="nav">
<li><a href="#">Item 1</a></li>
</ul>

Because each of the list items has a common parent, descendant selectors can simplify the CSS markup as follow: